Vacuum packaging is used for many different types of goods, but is particularly useful in packaging food stuffs, including meat items such as sausages, sliced sandwich meat, steaks, chops, and also other related items for retail distribution, including cheese, poultry, fish, various dairy products and bakery products, vegetables and fruit, and various powders and liquids in measured quantities.
In such vacuum packaging machines, a web of plastic film is drawn into the machine, heated and deep drawn to define compartments for containing the items to be packaged. The edges of the traveling plastic film have previously been carried in clips mounted on continuous roller chains. The use of such roller chains in close proximity to foodstuffs is quite unsatisfactory because the chains present an unsanitary condition which cannot easily be corrected. At best, health inspectors tolerate these conveyor chains upon which the edges of the plastic film are carried, in recognition that the industry has not previously had a suitable substitute for such roller chains in this type of a vacuum packaging machine.
The entire machine including such roller chains are steam cleaned daily in an effort to maintain a sanitary condition, and accordingly, it is almost impossible to lubricate the chains to make them operate properly. Rusting of the roller chains results, and the lack of lubrication oftentimes produces excessive wear causing stretching of the roller chains. As a result, frequent adjustments must be made and these chains must be periodically replaced.
In a vacuum packaging machine the adjustment problems occasioned by wear of the chain links soon become problems of major concern. Because of the long lengths of the chains utilized for moving the web of plastic along numerous work stations, a minute amount of wear at each chain link will accumulate to a substantial lengthening of the entire chain.
The numerous work stations include heating and shaping the plastic; loading the compartments, sometimes by machine; positioning the top or covering web of plastic; sealing the top web to the shaped web; cutting the continuous web into discrete packages; and punching holes in the edge portions of the packages. Accordingly, unintentional lengthening of the chains requires adjustment and re-indexing of the mechanism at all of these stations, which is a project of major proportion.